Single-frequency network

A single-frequency network, often abbreviated SFN, is a set of transmitters that broadcast the same signal at the same time on the same frequency. Neighbouring transmitters do not disturb each other, and a radio simply receives whichever is stronger or combines them.

DAB+ is designed to work this way. It means a multiplex can cover a large area on one block, and a listener driving through the area does not need to retune.

FM works differently. Neighbouring FM transmitters need different frequencies, so a listener on a long drive has to retune or rely on a feature such as RDS to find the next frequency.